Alright, fine Travis. You can try and build for another version of gcc.
diff --git a/.travis.yml b/.travis.yml
index 0f6acbf..dfe0441 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -33,7 +33,7 @@
 script:
   - rvm use $RUBY_VERSION
   - gem install bundler
-  - if [ -z "$USE_GCC" ] ; then ./tools/run_tests/prepare_travis.sh ; fi
+  - ./tools/run_tests/prepare_travis.sh
   - if [ ! -z "$USE_GCC" ] ; then export CC=gcc-$USE_GCC ; export CXX=g++-$USE_GCC ; fi
   - ./tools/run_tests/run_tests.py -l $TEST -t -j 16 -c $CONFIG -s 4.0
 after_success: